Alastor and Vox run into each other while Al is taking a walk, recovering from his battle with Adam. Vox tries to fight him, but in Alastors weakened state, he is reminded of how his old friend used to be, and instead invites him out. They spend time catching up, and having deep, albeit drunken chats.
Both have ulterior motives, but as their friendship grows into something more, and Vox tries to make a deal with Alastor, things get messy very quickly. Alastor wants to rekindle his friendship, while Vox is still very much in love with Al, and will do anything to keep him close.
Both are obsessed with controlling the other, and Alastor begins to act very out of character to get what he wants, willing to indulge in Vox's desire in order to gain control, but he begins to get too attached, and realizes he might not be as strong willed and independent as he thought he could be.
After defeating Adam, Lucifer can't stop rubbing Alastor's defeat in his face. Their bickering continues as per usual until an important figure shows up, throwing a wrench in things. Lucifer must make a difficult choice, and Alastor can't help but use this opportunity to take the king of Hell down a path of revenge and destruction, only for his plan to blow up epically in his face.
*Before ya'll come for me, in this fanfic Alastor is ace not aroace which for this specific version of him, means that he is okay with kissing and cuddling and he likes to bite necks and shoulders (cause cannibal, duh), but anything sexual is OFF THE TABLE.